Kerry's remarks were in response to Snowden's first television interview, broadcast by NBC, in which the technology expert recounts how he stole and leaked a trove of classified documents revealing the NSA's program of phone and Internet surveillance.

"I was trained as a spy in sort of the traditional sense of the word in that I lived and worked undercover overseas -- pretending to work in a job that I'm not -- and even being assigned a name that was not mine," Snowden says, in an excerpt of the interview released this week by NBC.

Snowden said he had worked covertly as "a technical expert" for the Central Intelligence Agency and the National Security Agency, as well as as a trainer for the Defense Intelligence Agency.

"I don't work with people. I don't recruit agents. What I do is I put systems to work for the United States. And I've done that at all levels from -- from the bottom on the ground all the way to the top," he said.

Snowden, who has been charged in the United States with espionage, was granted asylum by Russia in August 2013 after shaking the American intelligence establishment to its core with a series of leaks on mass surveillance in the United States and around the world.